1. Field of the Invention
The invention relates to methods for improving the efficiency of production of cotton plants. More specifically, novel compositions of media and incubation conditions for enhancing production of embryogenic callus and development of embryos are disclosed.
2. Description of Related Art
New technologies have allowed production of commercially viable transgenic crops and had significant economic impact on the agricultural industry. These advancements enable creation of new crop varieties containing desirable novel traits. For such traits to succeed in the market place, it is essential that the time to market be shortened as much as possible.
The development of genomics technologies has enabled identification and isolation of a large number of genes and has necessitated the need for reliable and efficient transformation production systems for testing the utility of these genes by transforming them into economically important crops such as cotton. Genetic engineering of plants is typically a multi-step process requiring transformation of plant cells and regeneration of transgenic plants. Plant cells are transformed by introducing a nucleic acid sequence that is typically integrated into the genome of the host cell; followed by regeneration of sexually competent plant from the transformed cells. In the case of cotton, this process typically includes steps of explant inoculation with Agrobacterium, undifferentiated callus formation, embryogenic callus induction, embryo induction, maturation and germination of embryo, and plant development.
Several methods are available for introducing nucleic acid sequences into plant cells and are well known in the art. Methods for transforming dicots primarily use Agrobacterium tumefaciens (reviewed in Potrykus, 1991). Transgenic plants reported include cotton (e.g. U.S. Pat. No. 5,004,863 and U.S. Pat. No. 5,159,135). These reports describe the overall regenerative process, including transformation and selection of a transformed plant tissue, induction of that tissue to form embryos, and germination of those embryos to form a plant. Various media compositions are reported to promote the process. However, embryogenesis has historically required several months or more.
U.S. Pat. Nos. 5,244,802, 5,583,036, and 5,695,999 disclose methods for regenerating cotton plants from somatic cells. Modified media compositions were reported to be useful at different stages of the regenerative process. More specifically, transformed plant tissue was grown in medium supplemented with glucose until phenolic secretions ceased, whereby the tissue was transferred to a medium supplemented with sucrose instead of glucose. Many of the cotton lines tested formed transgenic calli, but did not undergo embryogenesis and regenerate into a plant. U.S. Pat. No. 4,672,035 describes a process of regenerating cotton plants utilizing modifications in media composition.
The process of cotton transformation and regeneration of transformed cotton plants usually takes any where from 12 to 14 months. The major portion of this time is utilized in regeneration of cotton plants. Therefore, an unmet need exists in the art for improved methods for the transformation and regeneration of cotton plants. The present disclosure addresses such needs by providing improvements over published methods by reducing time or increasing efficiency for obtaining a cotton plant from cotton plant tissue.